Fix agent workspace file handlers

backend/agents/workspace_manager.py

@@ -129,6 +129,33 @@ class RunWorkspaceManager:
         )
         return asset_dir
 
+    def load_agent_file(
+        self,
+        *,
+        config_name: str,
+        agent_id: str,
+        filename: str,
+    ) -> str:
+        """Load one run-scoped agent workspace file."""
+        path = self.get_agent_asset_dir(config_name, agent_id) / filename
+        if not path.exists():
+            raise FileNotFoundError(f"File not found: {filename}")
+        return path.read_text(encoding="utf-8")
+
+    def update_agent_file(
+        self,
+        *,
+        config_name: str,
+        agent_id: str,
+        filename: str,
+        content: str,
+    ) -> None:
+        """Write one run-scoped agent workspace file."""
+        asset_dir = self.get_agent_asset_dir(config_name, agent_id)
+        asset_dir.mkdir(parents=True, exist_ok=True)
+        path = asset_dir / filename
+        path.write_text(content, encoding="utf-8")
+
     def initialize_default_assets(
         self,
         config_name: str,